Safety device for materials handling structures



Sept. 29, 1970 I NARUNS' 3,530,999

SAFETY'DEVICE FOR MATERIAL HANDLING STRUCTURES- Filed Dec. 1, 1967 unllnn INVENTOR Lei/nan; Naruns Attorney:

- w /WW United States Patent 3,530,999 SAFETY DEVICE FOR MATERIALS HANDLING STRUCTURES Laimons Naruns, Pittsburgh, Pa., assignor to Dravo Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 1, 1967, Ser. No. 687,227 Int. Cl. B66c 23/72; E02f 3/18 US. Cl. 21249 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to material handling structures having a mobile carriage with a turntable, a mast on the turntable, a boom mounted on the mast for movements in elevation, an outrigger structure mounted on the mast diametrically opposite the boom and a moveable counterweight suspended from the outrigger and connected to the boom to maintain a constant lifting force on the boom.

BACKGROUND OF THE INVENTION The invention relates to material handling structures having a boom member which is pivoted in elevation.

Prior art While the invention is useful with various types of material handling structures, the description herein will be illustrated in connection with a bucket wheel machine. Such machines are used in the stacking and reclaiming of large quantities of bulk materials, such as coal, at power plants and other industrial sites. -In modern installations the machines are automated to stack and reclaim in a programmed sequence. The machines generally comprise a mobile carriage having a turntable thereon and a superstructure mounted on the turntable to rotate therewith. The superstructure comprises a mast, a boom secured to the mast and pivotally mounted for movements in elevation, an outrigger assembly rigidly mounted on the mast diametrically opposite the boom, and various items of hoisting and control equipment "as is well known in the art. The boom is luffed with cables attached thereto and to a hoist mounted on the outrigger. In bucket wheel machines the bucket wheel is mounted on the outer end of the boom and a belt coveyor exending along the boom carries materials toward or away from the wheel when it is stacking or reclaiming respectively.

In order to maintain a proper balance of the machine in both loaded and unloaded conditions, the outrigger is provided with a fixed counterweight. Under normal conditions this counterweight is adequate to maintain the machine in a stable condition, however, the length and weight of the boom and the weight of the wheel at the end of the boom are such that a number of situations can occur which can cause damage to the machine and personnel, particularly in large machines having a boom which may be over 200 feet long.

.If the boom lutdng cables break the boom will fall to the ground or come to rest on a pile of material, thereby possibly damaging the boom, bucket, conveyor and other equipment. Now, once the boom weight is at rest, the machine is unbalanced and may tip over in the direction of the fixed counterweight further damaging the machine.

The boom may also inadvertently be lowered so that its weight rests on the ground or the pile with the same result that the machine will be unbalanced and tip over in the direction of the fixed counterweight. In automated machines this can easily happen upon failure of the sens- 3,530,999 Patented Sept. 29, 1970 SUMMARY OF THE INVENTION The present invention comprises a material handling structure having a mobile carriage, a turntable on the carriage, a mast mounted on the turntable, a boom extending radially from the mast and pivotally mounted thereon for movements in elevation, an outrigger assembly mounted on the mast diametrically opposite the boom, and a counterweight movably suspended from the outrigger and connected to the boom to provide a constant tension in a tie member, such as a cable, connecting the boom to the counterweight. The movable counterweight not only provides the overall balance of the machine during normal conditions, but keeps the machine in balance during abnormal conditions, such as before described. The boom can safely be rested on a pile or on the ground Without danger of overturning because the counterweight exerts a predetermined lifting force on the boom even when the lufling lines are slack. The luffing lines may fail and balance will still 'be maintained. Because the counterweight applies a constant lifting force to the boom the effective weight of the boom held by the luffing cables is reduced. Thus the lufiing motors may be of a lower horsepower, the combination being selected such that there is sufiicient horsepower available to lift the boom but insuflicient to enable the machine to pull itself over should the boom become buried in a pile. Likewise, smaller cables may be employed in the luffing lines since the movable counterweight tie members or cables carry part of the boom load at all times.

Erection problems are also simplified when the movable counterweight is used as opposed to a fixed counterweight.

DESCRIPTION OF THE DRAWING The drawing illustrates one embodiment of the invention showing the rigging of the movable counterweight on a bucket wheel machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing there is illustrated a material handling machine 10 of the type commonly known as a bucket wheel machine, which generally comprises a mobile carriage 11 and a superstructure 12. The superstructure generally comprises a turntable 13 rotatably mounted on the carriage, a vertically extending inast 14 mounted on the turntable for rotation therewith, a boom 15 pivotally mounted on the mast at 16 for movement in elevation, a bucket wheel 17 mounted on the end of the boom, and a rigid outrigger assembly, indicated generally at 18, mounted on the mast diametrically opposite the boom 15. On the outrigger there is a cab 19 which houses the lufiing motor or motors (not shown), various controls and a lufiing cable drum 20. Lulfing cables 21 are reeved around the drum 20, sheaves 22 near the top of mast 14 and sheaves 23 on the boom struts 24.

The foregoing is a general description of a bucket wheel machine, and as such machines are well known in the art, no further description of the construction and operation is considered necessary.

The present invention is directed to the combination With such a machine, of a..movable counterweight 25 suspended from a cable 26 reeved around sheaves 27 mounted on a counterweight guide frame 28 on; the outrigger 18. Cables 26 are further reeved around sheaves 29 on the outer end of mast 14 anda'nchored to the boom struts at 30.

Counterweight 25 may therefore ride up and down in guide 28 in response to boom movements in elevation so that there is a constant tension maintained at all times in the connecting cables 26 completely independently of the boom position in elevation or the condition of operation of the lufiing motor and luffing cables 21.

. The counterweight may be made of any suitable material, such as concrete, and its weight selected so as to apply a lifting force on the boom but insufiicient to elevate the dead weight of the'boom and bucket wheel assembly. The boom and counterweight should be located on opposite sides of the center of rotation of the machine so that the weight 25 can be effective both as a safety device as described and also to function in place of a fixed counterweight.

The described invention therefore provides a simple connecting means comprises a cable, and including a sheave near the top of the mast over which the cable is reeved.

3. In a material handling machine having a vertically extending mast, a boom pivotally mounted on the mast for movements in elevation, a rigid outrigger extending from the mast opposite the boom, and means for raising and lowering the boom, the improvement comprising,

(a) a cable,

(b) guide means on, the outrigger and on the mast, and

(c) a counterweight, the cable being connected at one end to the counterweight and at its other end to the boom and being'guided in the guide means and arranged so that the counterweight is movably suspended from the outrigger whereby to maintain a constant tension in the cable.

4. In a material handling apparatus having a supporting carriage, a turntable mounted on the carriage, a mast projecting vertically from the turntable, a boom assembly pivotally mounted on the mast for movements in elevation, an outrigger connected to and extending radially from the mast diametrically opposite the boom, and

hoist and cable means for raising and lowering the boom,

but unique arrangement for counterbalancing a material handling apparatus, such as the illustrated bucket Wheel machine, and for preventing upsetting of the machine under various conditions which/can occur.

I claim:

1. In a material handling apparatus -having a supporting carriage, a turntable mounted on the carriage, a mast projecting vertically from the turntable, a boom assembly pivotally mounted on the mast for movements in elevation, an outrigger connected to and extending HUGO o. SCHULZ,

the improvement comprising,

(a) a counterweight movably suspended from the outrigger, and (b) means connecting the counterweight to the boom whereby-the counterweight exerts a constant lifting force'on the boom.

References Cited UNITED STATES PATENTS 203,332 5/1878 Fleming et al. 214-142 X 660,511 10/1900 Hoover 214142 3,304,634 2/1967 Becker 2l249 X 3,334,759 8/1967 Ludwig 214-10 Primary Examiner Us. 01. X.R. 37 214-142 

